It's taken a lot of effort to get the background this even from frame to frame for an animation, but I think I've finally found a good process for doing so. After taking care of darks and flats in preprocessing in Nebulosity, I use the histogram equalize feature in that program on the frames I want to use. Then, it's on to PixInsight. Automatic background extraction and common color calibration settings work to take out all the light pollution from shooting from an urban area. Make sure to use "divide" rather than "subtract" for the background extraction. Then, use the screen transfer function to automatically adjust each image, transfer the parameters to the histogram stretch, and voila! Nice even light levels from frame to frame, even under variable transparency.
Asteroid 2015 TB145 - this animated GIF is 69 10 second exposures taken from Long Beach, CA, on 2015-10-31 from 075650UT to 081040UT. Here, the asteroid… - Thad Szabo - Google+
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